Soft sanitary tissue paper web products comprising nano-filaments

ABSTRACT

A soft sanitary tissue paper web comprising at least one ply is disclosed. The soft sanitary tissue paper web comprises from about 2% to about 56.5% by weight of the soft sanitary tissue paper web of a softwood pulp fiber mixture and from about 43.5% to about 99.9% by weight of the dry fiber basis of the soft sanitary tissue paper web of a hardwood pulp fiber mixture. The softwood pulp fiber mixture comprises from about 0% to about 56.4% by weight of the dry fiber basis of the soft sanitary tissue paper web of softwood pulp fiber; from about 0.05% to about 20.0% by weight of the dry fiber basis of the soft sanitary tissue paper web of cellulose nanofilaments; and, from about 0.05% to about 3.0% by weight of the dry fiber basis of the soft sanitary tissue paper web of strengthening additive.

FIELD OF THE INVENTION

The present disclosure relates to soft sanitary tissue paper webscomprising cellulose nano-filaments and/or blends of cellulosemicro-filaments and cellulose nano-filaments.

BACKGROUND OF THE INVENTION

Tissue/towel paper products such as facial tissues, paper towels, bathtissues, napkins and other similar products, are designed to includeseveral important properties. For example products should have goodbulk, good absorbency, a soft feel, and should have good strength anddurability. Unfortunately, when steps are taken to increase one propertyof the product, the other characteristics of the product are oftenadversely affected.

Formulators have for years attempted to balance the level of softwoodfibers in their paper structures to ensure adequate strength of theirstructures while at the same time trying to minimize the negative impacton softness, durability or absorbency generally resulting from higherlevels of softwood fibers. One example of the problem has been thatformulators of bath tissue products have been unable to reliably makeacceptable fibrous structures, for example multi-density structures madeby through-air-dried (“TAD”) processes, that contain less than 20% byweight softwood fibers on a dry fiber basis without requiring excessiverefining of the softwood fibers and/or adding excessive chemicalstrength agents to achieve the desired level of strength and/orreliability (avoid sheet breaks during making and/or processing).

Similarly, for paper toweling products, formulators work to develop newproducts that have higher in-use strength at lower or equal drystrength. However, as formulators use typical paper making processvariables to increase product in-use or wet strength, other consumerdesired attributes such as absorbency and/or softness typicallydecrease. The typical problem formulators struggle with for papertoweling is how to increase towel in use or wet strength whilemaintaining or improving softness and/or absorbency, or how to decreasesoftwood inclusion while maintaining total product strength and/or sheetflexibility. All of the normal paper making process variables availableto a papermaker for increasing strength, normally can negatively affectthe sheet feel and product absorbency.

Accordingly there continues to be a need for new fibrous paperstructures that further optimize the physical product performance oftissue and towel products that increase wet and dry strength withoutsacrificing as much softness, absorbency and paper making reliability.Such structures are especially valuable for multi-density paper makingstructures with non-limiting examples of such structures being throughair dried, Fabric Crepe. NTT, ATMOS and UCTAD processes.

SUMMARY OF THE INVENTION

The present disclosure provides for a soft sanitary tissue paper webcomprising at least one ply. The soft sanitary tissue paper webcomprises from about 2% to about 56.5% by weight of the soft sanitarytissue paper web of a softwood pulp fiber mixture and from about 43.5%to about 99.9% by weight of the dry fiber basis of the soft sanitarytissue paper web of a hardwood pulp fiber mixture. The softwood pulpfiber mixture comprises from about 0% to about 56.4% by weight of thedry fiber basis of the soft sanitary tissue paper web of softwood pulpfiber; from about 0.05% to about 20.0% by weight of the dry fiber basisof the soft sanitary tissue paper web of cellulose nanofilaments; and,from about 0.05% to about 3.0% by weight of the dry fiber basis of thesoft sanitary tissue paper web of strengthening additive.

The present disclosure also provides for a soft sanitary tissue paperweb comprising at least one ply. The soft sanitary tissue paper webcomprises from about 2% to about 56.5% by weight of by weight of the dryfiber basis of the soft sanitary tissue paper web of a softwood pulpfiber mixture, from about 0.05% to about 3.0% by weight of the by weightof the dry fiber basis of the soft sanitary tissue paper web ofstrengthening additive; and, from about 43.5% to about 99.9% by weightof the by weight of the dry fiber basis of the soft sanitary tissuepaper web of a hardwood pulp fiber mixture. The softwood pulp fibermixture comprises from about 0% to about 56.4% by weight of the dryfiber basis of the soft sanitary tissue paper web of a softwood pulpfiber; and, at least about 0.05% to about 20% by weight of the dry fiberbasis of the soft sanitary tissue paper web of a blend of cellulosemicro-filaments and cellulose nano-filaments. The blend of cellulosemicro-filaments and cellulose nano-filaments comprises at least about50% by weight of the blend of cellulose micro-filaments and cellulosenano-filaments of cellulose micro-filaments and cellulosenano-filaments; at least about 10% by weight of the blend of cellulosemicro-filaments and cellulose nano-filaments of intact fibrillatedfibers; and at least about 5% by weight of the blend of cellulosemicro-filaments and cellulose nano-filaments of cellulosic fines.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. is a schematic diagram of one embodiment of a process for makingan absorbent through-air dried tissue web product for use in the presentdisclosure.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a process for making absorbent tissueor towel paper webs. The processes of the present invention producefibrous structures that contains natural and/or man-made fibers andcellulose nanofilaments that allow enhanced properties and/or theability to greatly reduce softwood content without negatively affectingpaper machine run-ability, sheet strength and/or other desired sheetattributes. More particularly, the present invention relates toprocesses of making fibrous structures that contain long and shortnatural and/or man-made (regenerated cellulose) fibers, and wherebycellulose nanofilaments are added at a range of from about 0.05% toabout 20.0% weight percentage of the dry fiber basis of the sheet, tothe softwood stream, either before or after refining. In a preferredembodiment the cellulose nanofilaments are added to the softwood streamafter the stream has been combined with either temporary or permanentstrengthening additives to form a mixed aqueous softwood fiber stream.

For non-layered products this mixed aqueous softwood stream is mixedwith the other aqueous streams, including other natural fiber streams,synthetic fiber stream and other man-made (regenerated cellulose) fibermaterials, and fed to the paper machine for production of the paper web.Alternatively, for layered products the softwood fiber/cellulosenanofilament stream is fed to a layer or layers of the head box that areseparate from the hardwood or surface layer of the sheet. The formedaqueous fiber sheet is then dewatered and dried on the paper machine forthe production of the paper web.

As used herein, “Paper Product” refers to any formed, fibrous structureproducts, traditionally, but not necessarily, comprising cellulosefibers. In one embodiment, the paper products of the present inventioninclude absorbent towel products. In an alternative embodiment, thepaper products of the present invention include soft sanitary tissueproducts.

The paper product of the present disclosure refers to paper productscomprising paper tissue products or paper towel products. The disclosedpaper technology in general, includes but is not limited to,conventional felt pressed or conventional wet-pressed tissue papers,pattern densified tissue papers, wet creped tissue paper products,through-air dried tissue paper products whether creped or uncreped. Forexample, a paper making process of the present disclosure can utilizeadhesive creping, wet creping, double creping, embossing, wet-pressing,air pressing, through-air drying, creped through-air drying, uncrepedthrough-air drying, as well as other steps in forming the paper web.Some examples of such techniques are disclosed in U.S. Pat. Nos.4,529,480, 5,048,589, 5,399,412, 5,129,988, 5,494,554, 5,607,551,6,398,916, 7,744,726 and 8,388,803. When forming multi-ply tissueproducts, the separate plies can be made from the same process or fromdifferent processes as desired. For example, in one embodiment, tissueor towel webs may be creped through-air dried webs formed usingprocesses known the art.

To form such webs, an endless traveling forming fabric, suitablysupported and driven by rolls, receives the layered or non-layered papermaking stock issuing from the headbox. A vacuum box is disposed beneaththe forming fabric and is adapted to remove water from the fiber furnishto assist in forming a web. From the forming wire/fabric, a formed webis transferred to a second fabric by a vacuum assist or mechanicalmeans, and this second template may be either a wire, a felt, or a wovenfabric as long as the desired topography is created in the structure ofthe template. The use of a sheet forming template that creates a papermaking structure with a plurality of fiber enriched regions of highlocal basis weight interconnected with a plurality of lower local basisweight regions. The fabric is supported for movement around a continuouspath by a plurality of guide rolls. A pick up roll designed tofacilitate transfer of web from fabric to fabric may be included totransfer the web.

Preferably the formed web is dried, preferably by blowing heated airthrough the formed web and then by transfer to the surface of arotatable heated dryer drum, such as a Yankee dryer. The drying cylinderis optionally provided with a resinous protective coating layerunderneath the resinous adhesive coating composition. The resinousadhesive coating composition is preferably re-wettable. The process isoperated such that the adhesive coating is maintained to providesufficient wet tack strength upon the transfer of the web to the dryingcylinder to secure the web during drying. The adhesive resin coatingcomposition is also maintained such that the adhesive coatingcompositions pliant when dried such that the web may be removed from thedrying cylinder without significant sheet damage when drying isaccomplished. The web may be transferred to the Yankee directly from thethrough drying fabric, if the drying fabric has topography, orpreferably, transferred to an impression fabric which is then used totransfer the web to the Yankee dryer. The web is then removed from thedryer drum by a creping blade. The creping of the web further reducesinternal bonding within the web and increases softness and absorbency.

In other embodiments, the base web is formed by an uncreped through-airdried process. Related uncreped through-air dried tissue processes aredescribed for example, in U.S. Pat. Nos. 5,656,132 and 6,017,417.

The fibrous structures in accordance with the present invention may bein the form of through-air-dried fibrous structures, differentialdensity fibrous structures, differential basis weight fibrousstructures, wet laid fibrous structures, air laid fibrous structures,creped or uncreped fibrous structures, pattern-densified ornon-pattern-densified fibrous structures, compacted or un-compactedfibrous structures, double re-creped fibrous structures as well known inthe art as exemplified in U.S. Pat. Nos. 3,301,746, 3,974,025, 4,191,609and 4,637,859, 6,398,906. and 8,388,803.

As use herein, the phrase “papermaking furnish” refers to aqueousmixture of either cellulosic or non-cellulosic fibers, paper makingfunctional aids (strength, absorbency or softness improvement), fillersand other paper making process materials that are used to form thepapermaking web.

As used herein the phrase “percent (%) by weight of dry fiber basis”refers to the percentage relevant material referenced against the fullydried, “bone dry”, fibers and other materials with all water and othervolatile materials removed from the papermaking web.

“Fiber”, as used herein, means an elongate physical structure having anapparent length greatly exceeding it apparent diameter, i.e. a length todiameter ratio of at least about 10 and less than 200. Fibers having anon-circular cross-section and/or tubular shape are common; the“diameter” in this case may be considered to be the diameter of a circlehaving cross-sectional area equal to the cross-sectional area of thefiber. More specifically, as used herein, “fiber” refers to fibrousstructure-making fibers. The present invention contemplates the use of avariety of fibrous structure-making fibers, such as, for example,natural fibers, such as cellulose nanofilaments and/or wood pulp fibers,non-wood fibers or any suitable fibers and any combination thereof.

Wood fibers; often referred to as wood pulps are liberated from theirsource by any one of a number of chemical pulping processes familiar toone experienced in the art, including kraft (sulfate), sulfite,polysulfide, soda pulping, etc. Further, the fibers can be liberatedfrom their source using mechanical and semi-chemical processesincluding, for example, roundwood, thermomechanical pulp,chemo-mechanical pulp (CMP), chemi-thermomechanical pulp (CTMP),alkaline peroxide mechanical pulp (APMP), neutral semi-chemical sulfitepulp (NSCS), are also contemplated. The pulp can be whitened, ifdesired, by any one or combination of processes familiar to oneexperienced in the art including the use of chlorine dioxide, oxygen,alkaline peroxide, and so forth. Chemical pulps, however may bepreferred since they impart superior tactile feel and/or desired tissuesheet properties. Pulps derived from both deciduous trees (hereinafter,referred to “hardwood”) and coniferous trees (hereinafter, also referredto as “softwood”) may be utilized and/or fibers derived from non-woodyplants along with man-made fibers. The hardwood, softwood, and/ornon-wood fibers can be blended, or alternatively, can be deposited inlayers to provide a stratified and/or layered web. U.S. Pat. Nos.4,300,981 and 3,994,771 disclose layering of softwood and hardwoodfibers. Also applicable to the present invention are fibers derived fromrecycled paper, as well as other non-fibrous materials, such asadhesives used to facilitate the original papermaking and paperconverting.

The wood pulp fibers may be short (typical of hardwood fibers) or long(typical of softwood fibers and some non-wood fibers). Softwood fibersderived from the kraft process and originating from more-northernclimates may be preferred. These are often referred to as northernbleached softwood Kraft (NBSK) pulps. Softwoods are typically includedinto paper webs at a variety of levels dependent on the desired productand product features. For example, formulators include softwood fibersinto absorbent towel products at a level of from about 20% to about89.9%, preferably from about 30% from about 70%, more preferably fromabout 40% to about 60% by weight of the dry fiber basis of the towelproduct. Further, formulators include softwood fibers into soft sanitarytissue product at a level of below 56.4%, preferably from about 2% toabout 45%, more preferably from about 10% to about 35%, and even morepreferably from about 20% to about 30% by weight of the dry fiber basisof the tissue product.

Non-limiting examples of short hardwood fibers include fibers derivedfrom a fiber source selected from the group consisting of Acacia,Eucalyptus, Maple, Oak, Aspen, Birch, Cottonwood, Alder, Ash, Cherry,Elm, Hickory, Poplar, Gum, Walnut, Locust, Sycamore, Beech, Catalpa,Sassafras, Gmelin, Albizia, and Magnolia. Non-limiting examples ofsoftwood fibers include fibers deprived from Pine, Spruce, Fir, Tamarak,Hemlock, Cypress, and Cedar. Formulators may include hardwood fibersinto absorbent towel products at a level of from about 10% to about 55%,preferably from about 20% from about 50%, more preferably from about 30%to about 40% by weight of the dry fiber basis of the towel product.Further, formulators include hardwood fibers into soft sanitary tissueproduct at a level of from about 43.5% to about 99.9%, preferably fromabout 50% to about 80%, and more preferably from about 60% to about 70%by weight of the dry fiber basis of the tissue product.

Another paper making material contemplated within this invention is theinclusion of micro algae as taught in U.S. Pat. No. 8,298,374. Fortissues and towels, microalgae can be marine or freshwater microalgae.The microalgae can be selected from, but not limited to, non-motileunicellular algae, flagellates, diatoms and blue-green algae. Themicroalgae can be selected from, but not limited to, the families ofDunaliella, Chlorella, Tetraselmis, Botryococcus, Haematococcus,Phaeodactylum, Skeletonema, Chaetoceros, Isochrysis, Nannochloropsis,Nannochloris, Pavlova, Nitzschia, Pleurochrysis, Chlamydomas orSynechocystis. The microalgae will desirably have a size in the longestdimension of less than about 500 μm and preferably less than 300 andeven more preferably less than 200 The small size of micro algae coupledwith the high retention characteristics of cellulose nanofilamentscreate unique synergies and paper making applications/structures.

Recycle fiber may be added to the furnish in any amount. While anysuitable recycle fiber may be used, recycle fiber with relatively lowlevels of groundwood is preferred in many cases, for example, recyclefiber with less than 15% by weight lignin content, or less than 10% byweight lignin content may be preferred depending on the furnish mixtureemployed and the application.

“Fibrillated man-made non-cellulose fibers”, also possibly used in paperproduct and contemplated in this invention are formed by using acellulosic dope prepared via multiple solvents know by one skilled inthe art. This dope is spun into fibers which can be used or furtherfibrillated and incorporated into the absorbent sheet. Not to be limitedto theory, a synthetic cellulose such as lyocell is considered alongwith modified lyocell that has been reduced in size via refining andother methods to create smaller fibers and fiber segments. U.S. Pat. No.7,718,036 shows various considered solvents and the inclusion offibrillated losel in a tissue and towel structure. Fibrillated manmadenon-cellulose fibers may optionally be included in the towel or tissuepaper webs up to a level of up to about 20%, preferably up to a level ofup to about 10%, more preferably up to a level of up to about 5% andmore preferably up to a level of up to about 2.5%.

“Non-wood, natural fibrous” structure-making fibers can also be usefulin the present invention and can include animal fibers, mineral fibers,plant fibers, man-made spun fibers, and engineered fibrous elements suchas cellulose nanofilaments. Animal fibers may, for example be selectedfrom the group consisting of wool, silk, and mixtures thereof. The plantfibers may, for example, be derived from a plant selected from the groupconsisting of wood, cotton, cotton linters, flax, sisal, abaca, hemp,hesperaloe, jute, bamboo, bagasse, esparto grass, straw, jute, hemp,milkweed floss, kudzu, corn, sorghum, gourd, agave, trichomes, loofahand mixtures thereof. Non-wood, natural fibers may optionally beincluded in the towel or tissue paper webs up to a level of up to about20%, preferably up to a level of up to about 10%, more preferably up toa level of up to about 5% and more preferably up to a level of up toabout 2.5%.

The present disclosure also contemplates paper web products made fromthe present processes composed of greater levels of non-wood, naturalfibers, for example greater than about 10%, preferably greater thanabout 20%, more preferably greater than about 50%, and even morepreferably greater than about 75% by weight of the dry fiber basis ofthe paper web of non-wood fibers. As a result, the paper web can becomposed of primarily non-wood fiber mixed with other fiber componentsand/or necessary chemical products, to produce the web efficiently andto meet the consumer product requirements. Non-wood fibers contemplatedcan either be short, i.e. less than about 1.2 millimeters in length) orlong (i.e. greater than 1.2 millimeters in length) or used incombinations of fibers of different lengths, to achieve the desiredproducts. In these structures, the cellulose nanofilaments can be addedto either the long fiber or short fiber segment as desired to achievethe target product properties.

As used herein, the phrase “non-cellulosic fibers” means the group ofpaper making fibers that are composed of either natural or man-madefibers that are composed of materials other than cellulose.Non-cellulosic fibers include but are not limited to man-made spunfibers, fibers from animal sources, and/or micro-algae. Additionally,fibers forming the products of the present invention may be spun frompolymer melt compositions via suitable spinning operations, such asmelt-blowing and/or spin-bonding and/or they may be obtained fromnatural sources. Such fibers may be mono-component and/ormulticomponent. For example, the fibrous elements may comprisebicomponent fibers and/or filaments. The bicomponent fibers and/orfilaments may be in any form, such as side-by-side, core and sheath,islands-in-the-sea and the like. Non-limiting examples of filamentsinclude melt-blown and/or spun-bond filaments. Non-limiting examples ofpolymers that can be spun into filaments include natural polymers, suchas starch, starch derivatives, cellulose, such as rayon and/or lyocell,and cellulose derivatives, hemicellulose, hemicellulose derivatives, andsynthetic polymers including, but not limited to thermoplastic polymerfilaments, such as polyesters, nylons, polyolefins such as polypropylenefilaments, polyethylene filaments, and biodegradable thermoplasticfibers such as polylactic acid filaments, polyhydroxyalkanoatefilaments, polyesteramide filaments and polycaprolactone filaments.Non-limiting examples of fibers include pulp fibers, such as wood pulpfibers, and synthetic staple fibers such as polypropylene, polyethylene,polyester, copolymers thereof, rayon, glass fibers and polyvinyl alcoholfibers. Staple fibers may be produced by spinning a filament tow andthen cutting the two into segments of less than 5.08 cm (2 in.) thusproducing fibers. Non-cellulosic fibers may optionally be included inthe towel or tissue paper webs up to a level of up to about 20%,preferably up to a level of up to about 10%, more preferably up to alevel of up to about 5% and more preferably up to a level of up to about2.5%.

“Synthetic polymer fibers” and like terminology also refer tonon-cellulosic fibers made from synthetic polymers such as polyesters,nylons and polyolefins and so forth. Polyesters are generally obtainedby known polymerization techniques from aliphatic or aromaticdicarboxylic acids with saturated aliphatic or aromatic diols. Preferredaromatic diacid monomers are the lower alkyl esters such as the dimethylesters of terephthalic acid or isophthalic acid. Typical aliphaticdicarboxylic acids include adipic, sebacic, azelaic, dodecanedioic acidor 1,4-cyclohexanedicarboxylic acid. The preferred aromatic dicarboxylicacid or its ester or anhydride is esterified or trans-esterified andpoly-condensed with the saturated aliphatic or aromatic diol. Typicalsaturated aliphatic diols preferably include the lower alkane-diols suchas ethylene glycol. Typical cycloaliphatic diols include 1,4-cyclohexanediol and 1,4-cyclohexane dimethanol. Typical aromatic diols includearomatic diols such as hydroquinone, resorcinol and the isomers ofnaphthalene diol (1,5-; 2,6-; and 2,7-). Various mixtures of aliphaticand aromatic dicarboxylic acids and saturated aliphatic and aromaticdiols may also be used. Most typically, aromatic dicarboxylic acids arepolymerized with aliphatic diols to produce polyesters, such aspolyethylene terephthalate (terephthalic acid+ethylene glycol).Additionally, aromatic dicarboxylic acids can be polymerized witharomatic diols to produce wholly aromatic polyesters, such aspolyphenylene terephthalate (terephthalic acid+hydroquinone). Examplesof polyesters include; polyethylene terephthalate;poly(1,4-butylene)terephthalate; and 1,4-cyclohexylene dimethyleneterephthalate/isophthalate copolymer and other linear homopolymer estersderived from aromatic dicarboxylic acids, including isophthalic acid,bibenzoic acid, naphthalene-dicarboxylic acid including the 1,5-; 2,6-;and 2,7-naphthalene-dicarboxylic acids; 4,4,-diphenylene-dicarboxylicacid; bis(p-carboxyphenyl)methane acid; ethylene-bis-p-benzoic acid;1,4-tetramethylene bis(p-oxybenzoic) acid; ethylene bis(p-tetramethyleneacid; 1,3-trimethylene bis(p-oxybenzoic) acid; and 1,4-tetramethylenebis(p-oxybenzoic) acid, and diols selected from the group consisting of2,2-dimethyl-1,3-propane diol; cyclohexane dimethanol and aliphaticglycols of the general formula HO(CH2)_(n)OH where n is an integer from2 to 10, e.g., ethylene glycol; 1,4-tetramethylene glycol;1,6-hexamethylene glycol; 1,8-octamethylene glycol; 1,10-decamethyleneglycol; and 1,3-propylene glycol; and polyethylene glycols of thegeneral formula HO(CH2CH2O)_(n)H where n is an integer from 2 to 10,000,and aromatic diols such as hydroquinone, resorcinol and the isomers ofnaphthalene diol (1,5-; 2,6-; and 2,7). There can also be present one ormore aliphatic dicarboxylic acids, such as adipic, sebacic, azelaic,dodecanedioic acid or 1,4-cyclohexanedicarboxylic acid.

Suitable polyolefin resins include material made by polymerizing sucholefins as ethylene, propylene, butene-1, pentene-1,4-methylpent-1-ene,etc., in conventional manner. Useful polyolefins for fibers arehigh-density polyethylene (HDPE) and polypropylene. Other polyolefinhomopolymers and copolymers of ethylene can be utilized in the practiceof this invention. Such other polyolefins include low-densitypolyethylene (LDPE), very low-density polyethylene (VLDPE), linearlow-density polyethylene (LLDPE) and polybutylene (PB). However, theseother polyolefins can be blended with other polyolefins such aspolypropylene or high-density polyethylene (HDPE).

Nylon or polyamide resins useful in the practice of the invention arewell-known in the art and include semi-crystalline and amorphous resins,which may be produced for example by condensation polymerization ofequimolar amounts of saturated dicarboxylic acids containing from 4 to12 carbon atoms with diamines, by ring opening polymerization oflactams, or by copolymerization of polyamides with other components,e.g. to form polyether polyamide block copolymers. Examples ofpolyamides include polyhexamethylene adipamide (nylon 66),polyhexamethylene azelaamide (nylon 69), polyhexamethylene sebacamide(nylon 610), polyhexamethylene dodecanoamide (nylon 612),polydodecamethylene dodecanoamide (nylon 1212), polycaprolactam (nylon6), polylauric lactam, poly-11-aminoundecanoic acid, and copolymers ofadipic acid, isophthalic acid, and hexamethylene diamine.

Synthetic polymer fibers are generally hydrophobic as compared withcellulose and lack anionic sites for bonding to wet strength resins orenough hydroxyl groups to hydrogen bond effectively to pulp-derivedfiber. Suitable fibers used in connection with this invention includemelt-spun fibers, melt-blown fibers, splittable fibers having multiplesegments and especially segmented bicomponent fibers which aresplittable into their segments by refining in a disk refiner. Onesuitable fiber available from Fiber Innovation Technology is a16-segment, 2-denier nylon/polyester bicomponent fiber having acharacteristic fineness of 0.125 denier, discussed below.

Segmented fiber preparation for making splittable fibers is generallyknown in connection with thermoplastic fibers, where fibers havingsegments formed of different polymers. See, for example, U.S. Pat. No.5,759,926 to Pike et al., as well as U.S. Pat. No. 5,895,710 to Sasse etal. and United States Patent Application Publication No. 2003/0203695(U.S. patent application Ser. No. 10/135,650) of Polanco et al.

The splittable fibers produced and utilized in connection with thisinvention may have a segmented pie shape, an island in the seaconfiguration, a side-by-side configuration, a hollow configuration andso forth. See U.S. Pat. No. 4,735,849 to Murakami et al., FIGS. 6A-6D,as well as United States Patent Application Publication No. US2002/0168912 (U.S. patent application Ser. No. 09/852,888), FIGS. 2-9.Splittable fibers are suitably disintegrated prior to incorporation intothe furnish as is discussed below

During the preparation of fibers for the paper making operation,softwood fiber and some hardwood fiber pulps are subjected to mechanicalor chemical processing whereby the fibers are either compressed,subjected to high shear and/or chemically treated to make the fibersmore flexible and create increased fiber to fiber bonding area throughfiber fibrillation, fiber swelling and increased fiber flexibility.Those skilled in the art will recognize three predominate products ofrefining a pulp fiber are; 1) a percentage fibers are not impacted atall depending upon refining intensity and consistency, 2) a significantpercentage of fibers are fibrillated whereby the fiber cell wall isdelaminated and microfibrils are exposed that remain bound to theoriginal fiber, and 3) a percentage of fibers and microfibrils are cutor mechanically broken into very small pieces (<200 micron in length)and this fraction is referred to as the fines fraction. These fines caneither primary (those that exist in the native wood source) or secondary(those created during the act of refining). What has been discovered isthat that by altering refining intensity, consistency and otherprocessing conditions, a new fiber constituent can be created calledherein “cellulose nanofilaments” and by optimizing the processing stagesand unit operations a resultant pulp fiber stream containing greater 40%of individualized cellulose nanofilaments can be produced.

The “cellulose nanofilaments” used in the present invention may bederived from either softwood and/or hardwood and as such may containfibrous elements of the softwood or hardwood. The cellulosenanofilaments are used in the processes of making absorbent towels orsoft sanitary tissues in addition into the refined pulp fiber mixture ofthe papermaking furnish.

The cellulose nanofilaments are added at a level of from about 0.05% toabout 20.0%, preferably from about 0.1% to about 10.0%, more preferablyfrom about 0.2% to about 5%, and even more preferably from about 0.5 toabout 2% by weight of the dry fiber basis of the desired paper web.

In the processes contemplated in the present invention, the cellulosenanofilaments are preferably added to the refined softwood pulp fibermixture along with the softwood pulp fibers and the strengtheningadditive. In one embodiment the cellulose nanofilaments are added to thesoftwood pulp fiber mixture before the strengthening additive. In aseparate embodiment the cellulose nanofilaments are added to thesoftwood pulp fiber mixture after the strengthening additive.

The cellulose nanofilament size and high aspect ratio distinguish thismaterial as a unique fiber class and not characterized as either asoftwood or hardwood material. By high aspect ratio it is meant a fiberlength divided by fiber width of at least 200 to about 5000, preferablygreater than about 600 to about 1000. The cellulose nanofilament has anaverage width in the nanometer range, for example an average width ofabout 30 nm to about 500 nm, and an average length in the micrometerrange or above, for example an average length about 100 um, preferablefrom about 200 um to about 2 mm. The cellulose nanofilaments have anaverage thickness of from about 20 nm to about 60 nm, preferably fromabout 30 nm to about 50 nm, more preferably from about 35 nm to about 45nm. Such cellulose nanofilaments can be obtained, for example, from aprocess which uses mechanical means only, for example, the methodsdisclosed in U.S. patent application Publication no. 2013/0017394, fileJan. 19, 2012. In addition, cellulose nanofilaments can be made from avariety of processes as long as the specified geometry is maintained.Processes used to create cellulose nanofilaments include but are notlimited to modified refining equipment, homogenizers, sonic fibertreatment, and chemical fiber treatment including enzymatic fibermodification.

In the paper “Nanocellulose Patent Trends: A Comprehensive Review onPatents on Cellulose Nanocrystals, Microfibrillated and BacterialCellulose”, Charreau et al, Nanotechnology, 2013 7, 56-80, the authorreviews the various terms to refer to mircofibrillated cellulose (MFC)over the years and “cellulose nanofilaments” could fit into thesegeneral terms. The “cellulose nanofilament” material of the presentdisclosure is specifically the result of the process disclosed inpublication US20130017394 A1 entitled “Cellulose nanofilaments andmethod for their production”, Hua, X., et al. The material produced bythis process is unique in that the process disclosed produces cellulosenanofilaments with aspect ratios (Length/width) significantly higherthan previously disclosed materials.

The cellulose nanofilaments that are the basis to this invention arestructurally very different from other cellulose fibrils such asmicro-fibrillated cellulose (MFC) or nano-fibrillated cellulose (NFC)prepared using other methods for mechanical disintegration of wood pulpfibers in that they have at least 40%, preferably 75% and morepreferably 90% by weight of the filaments of the fibrillated cellulosematerial have a filament length up to 300-350 um and diameters ofapproximately 100-500 nm. The fibrillated cellulose material in MFCtypically has lengths shorter than 100 um while the fibrillatedcellulose material in NFC typically has lengths shorter than 1 um.However it should be recognized by those skilled in the art that in theproduction of cellulose nanofilaments material, like other fibrillatedcellulose materials produced using mechanical means are not homogeneousmaterial with one single dimension value. The cellulose nanofilaments inthe preferred embodiment have lengths of up to 300-350 um and diametersof approximately 100-500 nm and are produced by multiples, highconsistency refining of wood or plant fibers and with no less than 50%by weight of its cellulose nanofilaments having lengths of up to 300-350um and diameters of approximately 100-500 nm. The precise percentage ofthe cellulose nanofilaments material having lengths of up to 300-350 umand diameters of approximately 100-500 nm depends on the total energyinput, the number of refining passes, the refining intensity and otherrefining operating conditions. The cellulose nanofilament materialdescribed above and the preferred blend of a refined pulp streamcontaining >50% cellulose nanofilaments within a refined pulp stream arethe basis for this invention.

Another envisioned application of cellulose nanofilaments contemplatedin this invention is the inclusion of a small percentage of either purecellulose nanofilaments and/or a mixture of cellulose nanofilaments andother refining products to a virgin or recycled pulp stream before beingshipped to a paper making site. In this way a virgin fiber source can beenhanced via cellulose nanofilament addition and then the cellulosenanofilaments can be added to a paper making process without introducinga new fiber dosing stream. By dosing cellulose with cellulosenanofilaments at a pulp production facility one could produce what couldbe termed a “super pulp” with characteristics only possible throughcellulose nanofilament inclusion. Therefore many different methods forcellulose monofilament addition are considered in the invention andthese include but are not limited to direct pure cellulose nanofilamentinclusion, including a mixture of cellulose nanofilaments and otherrefining byproducts with a preferred nanocellulose content of >50% andcellulose nanofilaments being added via inclusion in virgin or recycledfiber before inclusion at the paper mill.

In alternative embodiments of the papermaking processes describedherein, and the paper products made by those processes, thenanofilaments are delivered to the process, and thereby the paper, in adry blend of micro- and nano-sized cellulose filaments. The blend maycomprise a blend of cellulose nanofilaments, intact fibrillated fibersand cellulosic fines.

The phrase “Intact fibrillated cellulose fibers” or “Intact fibrillatedfibers” as use herein, are cellulosic fibers that have undergonemechanical or chemical treatment during which individual or bundles ofcellulosic filaments are liberated from the body of the fiber but remainjoined to the fiber on one end creating more bonding area and increasedfiber to fiber contact. The degree of treatment determines the number ofcellulose nanofilaments that have been released from the fiber.

As used herein, the phrase “cellulosic fines”, means the class of fibersmaterials that have a length <200 microns. These materials can includeprimary, or naturally occurring materials in a tree, or they can beclassified as secondary, those created by either pulping and/or handlingof pulp fibers and therefore can contain fiber sections and/or cellulosenanofilaments sections. Fines are not a homogenous material and are onlyused to represent a class of material with a defined length limitation.

When a blend of micro- and nano-sized cellulose filaments is used, theblend may comprise at least about 40%, preferably at least about 60%,more preferably at least about 75% by weight of the blend of cellulosenanofilaments; at least about 10%, preferably at least about 20%, morepreferably at least about 30% by weight of the blend of intactfibrillated fibers; and at least about 5%, preferably at least about10%, more preferably at least about 20% by weight of the blend ofcellulosic fines.

The fibrous structure of the present invention may be homogeneous or maybe layered. If layered, the fibrous structures may comprise at least twoand/or at least three and/or at least four and/or at least five layers.

“Basis weight as used herein is the weight per unit area of a samplereported in lbs/3000 ft² or g/m². The fibrous towel structures and/orsanitary tissue products of the present invention may exhibit a basisweigh of between 10 g/m2 to about 120 g/m2 and/or from about 14 g/m2 toabout 80 g/m2 and/or from about 20 g/m2 to about 60 g/m2.

Basis weight is measured by preparing one or more samples of a certainarea (m²) and weighing the sample(s) of a fibrous structure according tothe present invention and/or a paper product comprising such fibrousstructure on a top loading balance with a minimum resolution of 0.01 g.The balance is protected from air drafts and other disturbances using adraft shield. Weights are recorded when the readings on the balancebecome constant. The average weight (g) is calculated and the averagearea of the samples (m²). The basis weight (g/m²) is calculated bydividing the average weight (g) by the average area of the samples (m²).

“Soft sanitary tissue product” as used herein means a soft low density(i.e. <about 0.15 g/cm3) web useful as a wiping implement forpost-urinary and post-bowel movement cleaning (toilet tissue), forotorhinolaryngological discharges (facial tissue), and multi-functionalabsorbent and cleaning uses (absorbent towels). The sanitary tissueproduct prepared according to the present disclosure may be subjected toany suitable post processing including, but not limited to printing,embossing, calendaring, slitting, folding, combining with other fibrousstructures and/or winding, and the like.

In one example of a soft tissue product of the present invention, thefibrous structure comprises from about 2% to 56.5% percent by weight ofa refined softwood pulp fiber mixture. The refined softwood fibermixture comprises from about 0% to about 56.4% by weight of the dryfiber basis of the soft tissue product of a soft wood pulp. The softwoodpulp is optionally refined or not refined prior to combination with astrengthening additive. The strengthening additive is added to theaqueous stream in a manner that enables from about 0.05% to about 1.5%by weight of the dry fiber basis of the tissue product of thestrengthening additive to be added to the paper making furnish. Aftercombination of the long fiber wood pulp and cationic polymer, from about0.05% to about 20.0% by weight of the dry fiber basis of the tissuepaper web of cellulose nanofilaments are blended into the stream. In oneembodiment of the invention this stream is then blended with about 43.5%to about 99.9% by weight of the dry fiber basis of the tissue product ofhardwood pulp fiber mixture including both hardwood fibers and cellulosenanofilaments and formed into the fibrous sheet by any the processesdiscussed above. In another embodiment of the invention, the long fiberstream is fed into a separate layer or layers of the paper making systemand isolated from the hardwood pulp fiber stream. This processembodiment produces a soft sanitary tissue product.

“Absorbent towel product” as used herein is a class of papermakingproduct that is designed and manufactured to meet the consumer need forliquid absorption and wet scrubbing along with soft hand feel. Absorbentproduct is made on the same paper making technology as sanitary tissueand facial tissue, but raw materials, paper making process setup, basisweight and other raw materials are optimized to deliver the desiredconsumer attributes.

In another example, a process for making an absorbent towel product, ofthe present invention the fibrous structure comprises from about 45% to90% percent by weight of a refined softwood pulp fiber mixture. The longfiber softwood pulp fiber mixture comprises from about 20% to about89.9% by weight of the dry fiber basis of the towel product of a longfiber soft wood pulp wherein the long fiber softwood pulp is optionallyrefined or not refined prior to combination with a strengtheningadditive. The strengthening additive is added to the aqueous stream in amanner that enables from about 0.05% to about 5.0% by weight of the dryfiber basis of the absorbent towel of strengthening additive to be addedto the paper making furnish. After combination of the softwood pulp andcationic polymer, from about 0.05% to about 20%, by weight of the dryfiber basis of the tissue paper web of cellulose nanofilaments areblended into the stream. In this embodiment of the invention thesoftwood fibers, cellulose nanofilament and cationic stream is thenblended with 10% to 55% by weight of the dry fiber basis of the towelproduct with of hardwood pulp fiber mixture and formed into the fibroussheet by any of the processes discussed above. In another embodiment ofthe invention, the long fiber stream is fed into a separate layer orlayers of the paper making system and isolated from the 10 to 55% byweight hardwood pulp fiber stream. This process embodiment produces ahigher strength absorbent tissue web product.

Strengthening additives—The processes of the present application alsocomprise the addition of a strengthening additive to the papermakingfurnish. Generally, strengthening additives may be applied in variousamounts, depending on the desired characteristics of the web. Forinstance, in some embodiments, the total wet strength agents added canbe between about 0.5 to 50 kg/T in some embodiments, between 2 to about15 kg/T, and in some embodiments, between about 3 to about 5 kg/T. Thestrength polymers can be incorporated into any layer of the multi-layertissue web.

The strengthening additives useful in this invention include withoutlimitation cationic water soluble resins. These resins impart wetstrength to paper sheets and are well known in paper making art. Suchresins include polyamide epichlorohydrin (PAE), urea-formaldehyderesins, melamine formaldehyde resins, polyacrylamide resins, dialdehydestarches, and mixtures thereof.

In some embodiments, other strength agents can be utilized to furtherenhance the strength of a tissue product. As used herein, a “wetstrength agent” is any material that, when added to pulp fibers canprovide a resulting web or sheet with a wet geometric tensile strengthto dry geometric tensile strength ration in excess of about 0.1.Typically these are termed either “permanent” wet strength or“temporary” wet strength agents. As is well known in the art, temporaryand permanent wet strength agents may also sometimes function as drystrength agents to enhance the strength of the tissue product when dry.The listing of optional chemical ingredients are intended to barelyexemplary in nature, and are not meant to limit the scope of theinvention. Other materials may be included as well so long as they donot interfere or counteract the advantages of the present invention.

Wet strength agents may be applied in various amounts, depending on thedesired characteristics of the web. For instance, in some embodiments,the total wet strength agents added can be between about 0.5 to 50 kg/Tin some embodiments, between 2 to about 15 kg/T, and in someembodiments, between about 3 to about 5 kg/T of the strength agents canbe incorporated into any layer of the multi-layer tissue web. Thecationic wet strength resins useful in this invention include withoutlimitation cationic water soluble resins. These resins impart wetstrength to paper sheets and are well known in paper making art. Thisresin may impart either temporary or permanent wet strength to thefibrous sheet. Such resins include polyamide epichlorohydrin (PAE),urea-formaldehyde resins, melamine formaldehyde resins, polyacrylamideresins, dialdehyde starches, and mixtures thereof.

The strength additive may be selected from the group consisting ofpermanent wet strength resins, temporary wet strength resins, drystrength additives, and mixtures thereof. If permanent wet strength isdesired, the chemical papermaking additive can be chosen from thefollowing group of chemicals: polyamidpichlorohydrin, polyacrylamides,insolubilized polyvinyl alcohol; ureaormaldehyde; polyethyleneimine; andchitosan polymers. Polyamideepichlorohydrin resins are cationic wetstrength resins which have been found to be of particular utility.Suitable types of such resins are described in U.S. Pat. No. 3,700,623,issued on Oct. 24, 1972, and U.S. Pat. No. 3,772,076, issued on Nov. 13,1973, both issued to Keim. One commercial source of a usefulpolyamideepichlorohydrin resins is Hercules, Inc. of Wilmington, Del.,which markets such resin under the trademark KYMENE® 557H.

Polyacrylamide resins have also been found to be of utility as wetstrength resins. These resins are described in U.S. Pat. No. 3,556,932,issued on Jan. 19, 1971, to Coscia, et al. and U.S. Pat. No. 3,556,933,issued on Jan. 19, 1971, to Williams et al. One commercial source ofpolyacrylamide resins is American Cyanamid Co. of Stanford, Conn., whichmarkets one such resin under the mark PAREZ® 631 NC.

Still other water-soluble cationic resins finding utility in thisinvention are urea formaldehyde and melamine formaldehyde resins. Themore common functional groups of these polyfunctional resins arenitrogen containing groups such as amino groups and methylol groupsattached to nitrogen. Polyethylenimine type resins may also find utilityin the present invention.

If temporary wet strength is desired, the chemical papermaking additivecan be chosen from the following group of chemicals: cationic dialdehydestarch-based resin (such as Caldas produced by Japan Carlet, NationalStarch 78-0080 or Cobond 1000, both produced by National Starch andChemical Corporation); and dialdehyde starch. Modified starch temporarywet strength resins are also described in U.S. Pat. No. 4,675,394,Solarek, et al. issued Jun. 23, 1987. Preferred temporary wet strengthresins include those described in U.S. Pat. No. 4,981,557 issued on Jan.1, 1991, to Bjorkquist. Another example of a preferred temporary wetstrength resin is PAREZ® 750B, a commercially available modifiedpolyacrylamide resin manufactured by CyTec. If dry strength is desired,the chemical papermaking additive can be chosen from the following groupof chemicals. Polyacrylamide (such as combinations of Cypro 514 andACCOSTRENGTH 711 produced by American Cyanamid of Wayne, N.J.); starch(such as corn starch or potato starch); polyvinyl alcohol (such asAIRVOL 540 produced by Air Products Inc of Allentown, Pa.); guar orlocust bean gums; and/or carboxymethyl cellulose (such as AQUALON CMC-Tfrom Aqualon Co., Wilmington, Del.). In general, suitable starch forpracticing the present invention is characterized by water solubility,and hydrophilicity. Exemplary starch materials include corn starch andpotato starch, albeit it is not intended to thereby limit the scope ofsuitable starch materials; and waxy corn starch that is knownindustrially as amioca starch is particularly preferred. Amioca starchdiffers from common corn starch in that it is entirely amylopectin,whereas common corn starch contains both amplopectin and amylose.Various unique characteristics of amioca starch are further described in“Amioca—The Starch From Waxy Corn”, H. H. Schopmeyer, Food Industries,December 1945, pp. 106-108 (Vol. pp. 1476-1478). The starch can be ingranular or dispersed form albeit granular form is preferred. The starchis preferably sufficiently cooked to induce swelling of the granules.More preferably, the starch granules are swollen, as by cooking, to apoint just prior to dispersion of the starch granule. Such highlyswollen starch granules shall be referred to as being “fully cooked.”The conditions for dispersion in general can vary depending upon thesize of the starch granules, the degree of crystallinity of thegranules, and the amount of amylose present. Fully cooked amioca starch,for example, can be prepared by heating an aqueous slurry of about 4%consistency of starch granules at about 190° F. (about 88° C.) forbetween about 30 and about 40 minutes. Other exemplary starch materialswhich may be used include modified cationic starches such as thosemodified to have nitrogen containing groups such as amino groups andmethylol groups attached to nitrogen, available from National Starch andChemical Company, (Bridgewater, N.J.). Such modified starch materialshave heretofore been used primarily as a pulp furnish additive toincrease wet and/or dry strength. However, when applied in accordancewith this invention by application to a tissue paper web they may havereduced effect on wet strength relative to wet-end addition of the samemodified starch materials. Considering that such modified starchmaterials are more expensive than unmodified starches, the latter havegenerally been preferred. These wet and dry strength resins may be addedto the pulp furnish in addition to being added by the process describedin this invention. It is to be understood that the addition of chemicalcompounds such as the wet strength and temporary wet strength resinsdiscussed above to the pulp furnish is optional and is not necessary forthe practice of the present development.

In preferred embodiments of the process of the present invention, thestrengthening additive is added to the furnish in an amount ranging fromabout 0.05% to about 5.0%, preferably from about 0.05% to about 3.0%,more preferably from about 0.1% to about 1.5%, even more preferably fromabout 0.5% to about 1.5% by weight of the dry fiber basis of theabsorbent towel or sanitary tissue product being produced. In general,processes to manufacture absorbent towel products add higher levels ofpolymers where the polymer is added up to about 5.0%, preferably up toabout 3.0% and more preferably up to about 1.5%. Conversely, processesto produce sanitary tissue products add slightly lower levels ofstrengthening polymers where the polymer if added up to about 3.0% andpreferably up to about 1.5%.

Optional Ingredients—Chemical Papermaking Additives:

If desired, various chemical additive compositions may optionally beused to further enhance consumer desired benefits such as softness,lower lint, absorbency, sheet flexibility, and temporary and/orpermanent wet strength. The chemical additives are selected from thegroup consisting of de-bonders, silicon softening additives, non-siliconsoftening additives, absorbency additives and aesthetic additives.

De-Bonders

A chemical de-bonder can also be applied to soften the web.Specifically, a chemical de-bonder can reduce the amount of hydrogenbond within one or more layers of the web, which results in a softerproduct. Depending upon the desired characteristics of the resultingtissue product, the de-bonder can be applied in an amount between 0% toabout 3.0%, preferably from about 0.1 to about 2.0% and more preferablyfrom about 0.5 to about 1.0% by weight of the dry fiber basis of thepaper web. The de-bonder can be incorporated into any layer of thesingle or multilayer tissue web.

Suitable de-bonders for use as softener additives in the presentinvention include both cationic and noncationic surfactants, withcationic surfactants being preferred. Noncationic surfactants includeanionic, nonionic, amphoteric, and zwitterionic surfactants. Preferably,the surfactant is substantially nonmigratory in situ after the tissuepaper has been manufactured in order to substantially obviatepost-manufacturing changes in the tissue paper's properties which mightotherwise result from the inclusion of surfactant. This may be achieved,for instance, through the use of surfactants having melt temperaturesgreater than the temperatures commonly encountered during storage,shipping, merchandising, and use of tissue paper product embodiments ofthe invention: for example, melt temperatures of about 50° C. or higher.

The level of noncationic surfactant applied to tissue paper webs toprovide the aforementioned softness/tensile benefit ranges from theminimum effective level needed for imparting such benefit, on a constanttensile basis for the end product, to about 2%: preferably between about0.01% and about 2% noncationic surfactant is retained by the web; morepreferably, between about 0.05% and about 1.0%; and, most preferably,between about 0.05% and about 0.3%. The surfactants preferably havealkyl chains with eight or more carbon atoms. Exemplary anionicsurfactants are linear alkyl sulfonates, and alkylbenzene sulfonates.Exemplary nonionic surfactants are alkylglycosides includingalkylglycoside esters such as CRODESTA® SL-40 which is available fromCroda, Inc. (New York, N.Y.); alkylglycoside ethers as described in U.S.Pat. No. 4,011,389, issued to W. K. Langdon, et al. on Mar. 8, 1977;alkylpolyethoxylated esters such as PEGOSPERSE® 200 ML available fromGlyco Chemicals, Inc. (Greenwich, Conn.); alkylpolyethoxylated ethersand esters such as NEODOLR 25-12 available from Shell Chemical Co;sorbitan esters such as SPAN 60 from ICI America, Inc, ethoxylatedsorbitan esters, propoxylated sorbitan esters, mixed ethoxylatedpropoxylated sorbitan esters, and polyethoxylated sorbitan alcohols suchas TWEEN 60 also from ICI America, Inc. Alkylpolyglycosides areparticularly preferred for use in the present invention. The abovelistings of exemplary surfactants are intended to be merely exemplary innature, and are not meant to limit the scope of the invention.

Silicons

If a chemical softener that functions primarily by imparting a lubricousfeel is desired a polysiloxane or “silicon” can be used. Depending uponthe desired characteristics of the resulting tissue product, the siliconcan be applied in an amount between 0% to about 3.0%, preferably fromabout 0.1 to about 2.0% and more preferably from about 0.5 to about 1.0%by weight of the dry fiber basis of the paper web. The silicon can beincorporated into any layer of the single or multilayer tissue web.Suitable silicon compounds for use in the present invention aredescribed in detail below.

The polysiloxane compounds preferably have monomeric siloxane units ofthe following structure:

wherein, R1 and R2, for each independent siloxane monomeric unit caneach independently be hydrogen or any alkyl, aryl, alkenyl, alkaryl,arakyl, cycloalkyl, halogenated hydrocarbon, or other radical. Any ofsuch radicals can be substituted or unsubstituted. R1 and R2 radicals ofany particular monomeric unit may differ from the correspondingfunctionalities of the next adjoining monomeric unit. Additionally, thepolysiloxane can be either a straight chain, a branched chain or have acyclic structure. The radicals R1 and R2 can additionally independentlybe other silaceous functionalities such as, but not limited tosiloxanes, polysiloxanes, silanes, and polysilanes. The radicals R1 andR2 may contain any of a variety of organic functionalities including,for example, alcohol, carboxylic acid, aldehyde, ketone and amine, amidefunctionalities, with amino functional silicone compounds beingpreferred. Exemplary alkyl radicals are methyl, ethyl, propyl, butyl,pentyl, hexyl, octyl, decyl, octadecyl, and the like. Exemplary alkenylradicals are vinyl, allyl, and the like. Exemplary aryl radicals arephenyl, diphenyl, naphthyl, and the like. Exemplary alkaryl radicals aretoyl, xylyl, ethylphenyl, and the like. Exemplary arakyl radicals arebenzyl, alpha-phenylethyl, beta-phenylethyl, alpha-phenylbutyl, and thelike. Exemplary cycloalkyl radicals are cyclobutyl, cyclopentyl,cyclohexyl, and the like. Exemplary halogenated hydrocarbon radicals arechloromethyl, bromoethyl, tetrafluorethyl, fluorethyl, trifluorethyl,trifluorotoyl, hexafluoroxylyl, and the like. References disclosingpolysiloxanes include U.S. Pat. No. 2,826,551, issued Mar. 11, 1958 toGeen; U.S. Pat. No. 3,964,500, issued Jun. 22, 1976 to Drakoff; U.S.Pat. No. 4,364,837, issued Dec. 21, 1982, Pader, U.S. Pat. No.5,059,282, issued Oct. 22, 1991 to Ampulski et al.; and British PatentNo. 849,433, published Sep. 28, 1960 to Woolston. Also, SiliconCompounds, pp 181-217, distributed by Petrarch Systems, Inc., 1984,contains an extensive listing and description of polysiloxanes ingeneral.

Softening Additives

Any surfactant other than the chemical papermaking additive emulsifyingsurfactant material, is hereinafter referred to as “surfactant,” and anysurfactant present as the emulsifying component of emulsified chemicalpapermaking additives is hereinafter referred to as “emulsifying agent”.The surfactant may be applied to the tissue paper alone orsimultaneously with, after, or before other chemical papermakingadditives. In a typical process, if another additive is present, thesurfactant is applied to the cellulosic substrate simultaneously withthe other additive(s). It may also be desirable to treat a de-bondercontaining tissue paper with a relatively low level of a binder for lintcontrol and/or to increase tensile strength.

If a chemical softener that functions primarily by imparting a lubricousfeel is desired, it can be chosen from the following group of chemicals.Organic materials (such as mineral oil or waxes such as paraffin orcarnuba, or lanolin); and polysiloxanes (such as the compounds describedin U.S. Pat. No. 5,059,282 issued to Ampulski). Suitable polysiloxanecompounds for use in the present invention are described in detailbelow.

If a chemical softener that functions primarily by plasticizing thestructure is desired, it can be chosen from the following group ofchemicals: polyethylene glycol (such as PEG 400); dimethylamine; and/orglycerin.

If a cationic chemical softener that functions primarily by debonding isdesired, it can be chosen from the following group of chemicals.Cationic quaternary ammonium compounds (such as dihydrogenated tallowdimethyl ammonium methyl sulfate (DTDMAMS) or dihydrogenated tallowdimethyl ammonium chloride (DTDMAC) both produced by Witco Corporationof Greenwich, Conn.; Berocel 579 (produced by Eka Nobel of Stennungsund,Sweden); materials described in U.S. Pat. Nos. 4,351,699 and 4,447,294issued to Osborn; and/or diester derivatives of DTDMAMS or DTDMAC.) Inparticular, quaternary ammonium compounds having the formula:

(R₁)_(4-m)−N⁺−[R2]_(m)X⁻

m is 1 to 3;

each R₁ is a C₁-C₈ alkyl group, hydroxyalkyl group, hydrocarbyl orsubstituted hydrocarbyl group, alkoxylated group, benzyl group, ormixtures thereof; each R₂ is a C₉-C₄₁ alkyl group, hydroxyalkyl group,hydrocarbyl or substituted hydrocarbyl group, alkoxylated group, benzylgroup, or mixtures thereof and X⁻ is any softener-compatible anion aresuitable for use in the present invention. Preferably, each R₂ isC₁₆-C₁₈ alkyl, most preferably each R₂ is straight-chain C₁₈ alkyl.Preferably, each R₁ is methyl and X⁻ is chloride or methyl sulfate.Optionally, the R₂ substituent can be derived from vegetable oilsources. Biodegradable ester-functional quaternary ammonium compoundhaving the formula:

(R₁)_(4-m)−N⁺−[(CH₂)_(n)—Y—R₂]_(m)X⁻

each Y═—O—(O)C—, or —C(O)—O—;m=1 to 3; preferably, m=2;each n=1 to 4; preferably, n=2;each R₁ substituent is a short chain C₁-C₆, preferably C₁-C₃, alkylgroup, e.g., methyl (most preferred), ethyl, propyl, and the like,hydroxyalkyl group, hydrocarbyl group, benzyl group or mixtures thereof;each R₂ is a long chain, at least partially unsaturated (IV of greaterthan about 5 to less than about 100, preferably from about 10 to about85), C₁₁-C₂₃ hydrocarbyl, or substituted hydrocarbyl substituent and thecounter-ion, X⁻, can be any softener compatible anion, for example,acetate, chloride, bromide, methylsulfate, formate, sulfate, nitrate andthe like can also be used in the present invention. Preferably, themajority of R₂ comprises fatty acyls containing at least 90% C₁₈-C₂₄chainlength. More preferably, the majority of R₂ is selected from thegroup consisting of fatty acyls containing at least 90% C₁₈, C₂₂ andmixtures thereof.

Other types of suitable quaternary ammonium compounds are described inEuropean Patent No. 0 688 901 A2, assigned to Kimberly-ClarkCorporation, published Dec. 12, 1995.

Tertiary amine softening compounds can also be used in the presentinvention. Examples of suitable tertiary amine softeners are describedin U.S. Pat. No. 5,399,241, assigned to James River Corporation, issuedMar. 21, 1995.

Absorbency Additives

If enhanced absorbency is desired, surfactants may be used to treat thepaper webs of the present invention. The level of surfactant, if used,in one embodiment, can be from about 0.01% to about 2% by dry fiberweight basis of the tissue web. In one embodiment the surfactants havealkyl chains with eight or more carbon atoms. Alternatively, cationicsoftener active ingredients with a high degree of unsaturated (monoand/or poly) and/or branched chain alkyl groups can greatly enhanceabsorbency.

If an absorbency aid is desired that enhances the rate of absorbency itcan be chosen from the following group of chemicals: polyethoxylates(such as PEG 400); alkyl ethoxylated esters (such as PEGOSPERSE 200 MLfrom Lonza Inc.); alkyl ethoxylated alcohols (such as Neodol); alkylpolyethoxylated nonylphenols (such as IGEPAL CO produced byRhone-Poulenc/GAF), ethoxylate trimethyl pentanediol, and/or materialsdescribed in U.S. Pat. Nos. 4,959,125 and 4,940,513 issued to Spendel.In those instances where the surfactant debonder softener decreaseswetting, a wetting agent, e.g., a second surfactant, may be added to theapplication solution. For example, a sorbitan stearate ester can bemixed with an alkyl polyethoxylated alcohol to produce a soft wettablepaper.

Water soluble polyhydroxy compounds can also be used as absorbency aidsand/or wetting agents. Examples of water soluble polyhydroxy compoundssuitable for use in the present invention include glycerol,polyglycerols having a weight average molecular weight of from about 150to about 800 and polyoxyethylene and polyoxypropylene having aweight-average molecular weight of from about 200 to about 4000,preferably from about 200 to about 1000, most preferably from about 200to about 600. Polyoxyethylene having an weight average molecular weightof from about 200 to about 600 are especially preferred. Mixtures of theabove-described polyhydroxy compounds may also be used. For example,mixtures of glycerol and polyglycerols, mixtures of glycerol andpolyoxyethylenes, mixtures of polyglycerols and polyoxyethylenes, etc.are useful in the present invention. A particularly preferredpolyhydroxy compound is polyoxyethylene having an weight averagemolecular weight of about 400. This material is available commerciallyfrom the Union Carbide Company of Danbury, Conn. under the trade name“PEG-400”.

If an absorbency aid is desired that decreases the rate of absorbency itcan be chosen from the following group of chemicals. Alkylketenedimers(such as AQUAPELR 360XC Emulsion manufactured by Hercules Inc.,Wilmington, Del.); fluorocarbons (such as Scotch Guard by 3M ofMinneapolis, Minn.) hydrophobic silicones (such as PDMS DC-200 by DowCorning of Midland, Mich.), fluorotelomers (such as ZONYL 7040 by Dupontof Wilmington, Del.), etc.

The absorbency additive can be used alone or in combination with astrength additive. Starch based strength additives have been found to bethe preferred binder for use in the present invention. Preferably, thetissue paper is treated with an aqueous solution of starch. In additionto reducing linting of the finished tissue paper product, low levels ofstarch also imparts a modest improvement in the tensile strength oftissue paper without imparting boardiness (i.e., stiffness) which wouldresult from additions of high levels of starch. Also, this providestissue paper having improved strength/softness relationship compared totissue paper which has been strengthened by traditional methods ofincreasing tensile strength: for example, sheets having increasedtensile strength due to increased refining of the pulp; or through theaddition of other dry strength additives. This result is especiallysurprising since starch has traditionally been used to build strength atthe expense of softness in applications wherein softness is not animportant characteristic: for example, paperboard. Additionally,parenthetically, starch has been used as a filler for printing andwriting paper to improve surface printability.

Aesthetic Additives

If an aesthetic additive is desired, it can be chosen from the followinggroup of chemicals: inks; dyes; perfumes; opacifiers (such as TiO2 orcalcium carbonate), optical brighteners, and mixtures thereof. Theaesthetics of the paper can also be improved utilizing the processdescribed in this invention. Inks, dyes, and/or perfumes are preferablyadded to the aqueous composition which is subsequently applied to thetissue paper web. The aesthetics additive may be applied alone or incombination with the wetting, softening, and/or strength additives.

Process for Making

In FIG. 1, a twin wire former having a papermaking headbox 1 injects ordeposits a furnish of an aqueous suspension of papermaking fibers onto aplurality of forming fabrics, such as the outer forming fabric 5 and theinner forming fabric 3, thereby forming a wet tissue web 6. The formingprocess of the present disclosure may be any conventional formingprocess known in the papermaking industry. Such formation processesinclude, but are not limited to, Fourdriniers, roof formers such assuction breast roll formers, and gap formers such as twin wire formersand crescent formers.

The wet tissue web 6 forms on the inner forming fabric 3 as the innerforming fabric 3 revolves about a forming roll 4. The inner formingfabric 3 serves to support and carry the newly-formed wet tissue web 6downstream in the process as the wet tissue web 6 is partially dewateredto a consistency of about 10 percent based on the dry weight of thefibers. Additional dewatering of the wet tissue web 6 may be carried outby known paper making techniques, such as vacuum suction boxes, whilethe inner forming fabric 3 supports the wet tissue web 6. The wet tissueweb 6 may be additionally dewatered to a consistency of at least about20 percent, more specifically between about 20 to about 40 percent, andmore specifically about 20 to about 30 percent.

The forming fabric 3 can generally be made from any suitable porousmaterial, such as metal wires or polymeric filaments. For instance, somesuitable fabrics can include, but are not limited to, Albany 84M and 94Mavailable from Albany International (Albany, N.Y.) Asten 856, 866, 867,892, 934, 939, 959, or 937; Asten Synweve Design 274, all of which areavailable from Asten Forming Fabrics, Inc. (Appleton, Wis.); and Voith2164 available from Voith Fabrics (Appleton, Wis.). Forming fabrics orfelts comprising nonwoven base layers may also be useful, includingthose of Scapa Corporation made with extruded polyurethane foam such asthe Spectra Series.

The wet web 6 is then transferred from the forming fabric 3 to atransfer fabric 8 while at a solids consistency of between about 10 toabout 40 percent, and particularly, between about 20 to about 30percent. As used herein, a “transfer fabric” is a fabric that ispositioned between the forming section and the drying section of the webmanufacturing process.

Transfer to the transfer fabric 8 may be carried out with the assistanceof positive and/or negative pressure. For example, in one embodiment, avacuum shoe 9 can apply negative pressure such that the forming fabric 3and the transfer fabric 8 simultaneously converge and diverge at theleading edge of the vacuum slot. Typically, the vacuum shoe 9 suppliespressure at levels between about 10 to about 25 inches of mercury. Asstated above, the vacuum transfer shoe 9 (negative pressure) can besupplemented or replaced by the use of positive pressure from theopposite side of the web to blow the web onto the next fabric. In someembodiments, other vacuum shoes can also be used to assist in drawingthe fibrous web 6 onto the surface of the transfer fabric 8.

Typically, the transfer fabric 8 travels at a slower speed than theforming fabric 3 to enhance the MD and CD stretch of the web, whichgenerally refers to the stretch of a web in its cross (CD) or machinedirection (MD) (expressed as percent elongation at sample failure). Forexample, the relative speed difference between the two fabrics can befrom about 1 to about 30 percent, in some embodiments from about 5 toabout 20 percent, and in some embodiments, from about 10 to about 15percent. This is commonly referred to as “rush transfer”. During “rushtransfer”, many of the bonds of the web are believed to be broken,thereby forcing the sheet to bend and fold into the depressions on thesurface of the transfer fabric 8. Such molding to the contours of thesurface of the transfer fabric 8 may increase the MD and CD stretch ofthe web. Rush transfer from one fabric to another can follow theprinciples taught in any one of the following patents, U.S. Pat. Nos.5,667,636, 5,830,321, 4,440,597, 4,551,199, 4,849,054.

The wet tissue web 6 is then transferred from the transfer fabric 8 to athrough-air drying fabric 11. Typically, the transfer fabric 8 travelsat approximately the same speed as the through-air drying fabric 11.However, it has now been discovered that a second rush transfer may beperformed as the web is transferred from the transfer fabric 8 to athrough-air drying fabric 11. This rush transfer is referred to hereinas occurring at the second position and is achieved by operating thethrough-air drying fabric 11 at a slower speed than the transfer fabric8. By performing rush transfer at two distinct locations, i.e., thefirst and the second positions, a tissue product having increased CDstretch may be produced.

In addition to rush transferring the wet tissue web from the transferfabric 8 to the through-air drying fabric 11, the wet tissue web 6 maybe macroscopically rearranged to conform to the surface of thethrough-air drying fabric 11 with the aid of a vacuum transfer roll 12or a vacuum transfer shoe like the vacuum shoe 9. If desired, thethrough-air drying fabric 11 can be run at a speed slower than the speedof the transfer fabric 8 to further enhance MD stretch of the resultingabsorbent tissue product. The transfer may be carried out with vacuumassistance to ensure conformation of the wet tissue web 6 to thetopography of the through-air drying fabric 11.

The processes of the present disclosure comprise the step of drying therespective webs until the web contains not more than about 10%,preferably not more than about 8%, more preferably not more than about6% by weight moisture.

While supported by the through-air drying fabric 11, the wet tissue web6 is dried to a final consistency of about 94 percent or greater by athrough-air dryer 13. The web 15 then passes through the winding nipbetween the reel drum 22 and the reel 23 and is wound into a roll oftissue 25 for subsequent converting, such as slitting cutting, folding,and packaging.

The web is transferred to the through-air drying fabric for final dryingpreferably with the assistance of vacuum to ensure macroscopicrearrangement of the web to give the desired bulk and appearance. Theuse of separate transfer and through-air drying fabrics can offervarious advantages since it allows the two fabrics to be designedspecifically to address key product requirements independently. Forexample, the transfer fabrics are generally optimized to allow efficientconversion of high rush transfer levels to high MD stretch whilethrough-air drying fabrics are designed to deliver bulk and CD stretch.It is therefore useful to have moderately coarse and moderatelythree-dimensional transfer fabrics and through-air drying fabrics whichare quite coarse and three dimensional in the optimized configuration.The result is that a relatively smooth sheet leaves the transfer sectionand then is macroscopically rearranged (with vacuum assist) to give thehigh bulk, high CD stretch surface topology of the through-air dryingfabric. Sheet topology is completely changed from transfer tothrough-air drying fabric and fibers are macroscopically rearranged,including significant fiber-fiber movement.

The drying process can be any non-compressive or compressive dryingmethod which tends to preserve the bulk or thickness of the wet webincluding, without limitation, through-air drying, infra-red radiation,microwave drying, Valmet NTT, Voith ATMOS, etc. Because of itscommercial availability and practicality, through-air drying is wellknown and is one commonly used means for non-compressively drying theweb for purposes of this invention. Suitable through-air drying fabricsinclude, without limitation, fabrics with substantially continuousmachine direction ridges whereby the ridges are made up of multiple warpstrands grouped together, such as those disclosed in U.S. Pat. No.6,998,024. Other suitable through-air drying fabrics include thosedisclosed in U.S. Pat. No. 7,611,607, particularly the fabrics denotedas Fred (t1207-77), Jeston (t1207-6) and Jack (t1207-12). The web ispreferably dried to final dryness on the through-air drying fabric,without being pressed against the surface of a Yankee dryer, and withoutsubsequent creping.

Once the wet tissue web 6 has been non-compressively dried, therebyforming the dried tissue web 15, it is possible to crepe the driedtissue web 15 by transferring the dried tissue web 15 to a Yankee dryerprior to reeling, or using alternative foreshortening methods such asmicro-creping as disclosed in U.S. Pat. No. 4,919,877.

In the wound product, it is often advantageous to wind the product withthe softest side facing the consumer, and hence the shearing process toincrease the softness of this side is preferred. However, it is alsopossible to treat the air side of the web rather than the fabric side,and in these embodiments, it would be possible to increase the air-sidesoftness to a level higher than that of the fabric side.

The process of the present disclosure is well suited to formingmulti-ply tissue products. The multi-ply tissue products can contain twoplies, three plies, or a greater number of plies. In one particularembodiment, a two-ply rolled tissue product is formed according to thepresent disclosure in which both plies are manufactured using the samepapermaking process, such as, for example, un-creped through-air dried.However, in other embodiments, the plies may be formed by two differentprocesses. Generally, prior to being wound in a roll, the first ply andthe second ply are attached together. Any suitable manner for laminatingthe webs together may be used. For example, the process includes acrimping device that causes the plies to mechanically attach togetherthrough fiber entanglement. In an alternative embodiment, however, anadhesive may be used in order to attach the plies together.

Additionally, webs prepared according to the present disclosure may besubjected to any suitable post processing including, but not limited to,printing, embossing, calendaring, slitting, folding, combining withother fibrous structures, and the like.

What is claimed is:
 1. A soft sanitary tissue paper web comprising at least one ply, said soft sanitary tissue paper web comprising: a) from about 2% to about 56.5% by weight of said soft sanitary tissue paper web of a softwood pulp fiber mixture, said softwood pulp fiber mixture comprising: 1) from about 0% to about 56.4% by weight of the dry fiber basis of said soft sanitary tissue paper web of softwood pulp fiber; 2) from about 0.05% to about 20.0% by weight of the dry fiber basis of said soft sanitary tissue paper web of cellulose nanofilaments; and, 3) from about 0.05% to about 3.0% by weight of the dry fiber basis of said soft sanitary tissue paper web of strengthening additive; and, b) from about 43.5% to about 99.9% by weight of the dry fiber basis of said soft sanitary tissue paper web of a hardwood pulp fiber mixture.
 2. The soft sanitary tissue paper web of claim 1 wherein said softwood pulp fiber is refined.
 3. The soft sanitary tissue paper web of claim 1 further comprising up to about 20% by weight of the dry fiber basis of said soft sanitary tissue paper web of a fiber selected from the group consisting of fibrillated man-made cellulose, non-wood natural fibers, non-cellulosic fibers, and combinations thereof.
 4. The soft sanitary tissue paper web of claim 1 further comprising greater than about 1.0% by weight of a chemical papermaking additive selected from the group consisting of debonders, silicons, softening additives, absorbency additives, aesthetic additives, and combinations thereof.
 5. The soft sanitary tissue paper web of claim 1 wherein said soft sanitary tissue paper web comprises at least two plies.
 6. The soft sanitary tissue paper web of claim 5 wherein said absorbent towel paper web comprises at least three plies.
 7. The soft sanitary tissue paper web of claim 6 wherein said absorbent towel paper web comprises at least four plies.
 8. The absorbent towel paper web of claim 1 wherein said cellulose nanofilaments are high aspect ratio cellulose nanofilaments.
 9. The absorbent towel paper web of claim 1 further comprising from about 0.1% to about 10% by weight of the dry fiber basis of said absorbent towel paper web of said cellulose nanofilaments.
 10. The absorbent towel paper web of claim 1 further comprising: a) from 0% to about 3.0% by weight of the dry fiber basis of said absorbent towel paper web of a debonder; and, b) from 0% to about 3.0% by weight of the dry fiber basis of said absorbent towel paper web of a silicon.
 11. A soft sanitary tissue paper web comprising at least one ply, said soft sanitary tissue paper web comprising: (a) from about 2% to about 56.5% by weight of by weight of the dry fiber basis of said soft sanitary tissue paper web of a softwood pulp fiber mixture, said softwood pulp fiber mixture comprising: 1) from about 0% to about 56.4% by weight of the dry fiber basis of said soft sanitary tissue paper web of a softwood pulp fiber; and, 2) at least about 0.05% to about 20% by weight of the dry fiber basis of said soft sanitary tissue paper web of a blend of cellulose micro-filaments and cellulose nano-filaments, wherein said blend of cellulose micro-filaments and cellulose nano-filaments comprises: A) at least about 50% by weight of said blend of cellulose micro-filaments and cellulose nano-filaments of cellulose micro-filaments and cellulose nano-filaments; B) at least about 10% by weight of said blend of cellulose micro-filaments and cellulose nano-filaments of intact fibrillated fibers; and C) at least about 5% by weight of said blend of cellulose micro-filaments and cellulose nano-filaments of cellulosic fines; and, b) from about 0.05% to about 3.0% by weight of the by weight of the dry fiber basis of said soft sanitary tissue paper web of strengthening additive; and, c) from about 43.5% to about 99.9% by weight of the by weight of the dry fiber basis of said soft sanitary tissue paper web of a hardwood pulp fiber mixture.
 12. The soft sanitary tissue paper web of claim 11 wherein said softwood pulp fiber is refined.
 13. The soft sanitary tissue paper web of claim 11 further comprising up to about 20% by weight of the dry fiber basis of said soft sanitary tissue paper web of a fiber selected from the group consisting of fibrillated man-made cellulose, non-wood natural fibers, non-cellulosic fibers, and combinations thereof.
 14. The soft sanitary tissue paper web of claim 11 wherein said softwood pulp fiber mixture further comprises greater than about 1.0% by weight of the dry fiber basis of said soft sanitary tissue paper web of a chemical papermaking additive selected from the group consisting of debonders, silicons, softening additives, absorbency additives, aesthetic additives, and combinations thereof.
 15. The soft sanitary tissue paper web of claim 11 wherein said soft sanitary tissue paper web comprises at least two plies.
 16. The soft sanitary tissue paper web of claim 15 wherein said soft sanitary tissue paper web comprises at least three plies.
 17. The soft sanitary tissue paper web of claim 16 wherein said soft sanitary tissue paper web comprises at least four plies.
 18. The soft sanitary tissue paper web of claim 11 wherein said cellulose micro-filaments and cellulose nano-filaments are high aspect ratio cellulose micro-filaments and cellulose nano-filaments.
 19. The soft sanitary tissue paper web of claim 11 further comprising from about 0.1% to about 10% by weight of the dry fiber basis of said absorbent towel paper web of said cellulose micro-filaments and cellulose nano-filaments.
 20. The soft sanitary tissue paper web of claim 11 further comprising: a) from 0% to about 3.0% by weight of the dry fiber basis of said absorbent towel paper web of a debonder; and, b) from 0% to about 3.0% by weight of the dry fiber basis of said absorbent towel paper web. 